1. Field of the Invention
The present invention relates to a radiographic imaging device and a radiographic imaging system using the same.
2. Description of the Related Art
In the medical field, a radiographic imaging device which images the inside of a human body by irradiating the human body with radiation, such as X-rays and detecting the intensity of the radiation transmitted into the human body is used. Examples of such a radiographic imaging device include a system including first directing incident light from radiation transmitted into a human body to a phosphor body, converting the same to visible light, converting the visible light to an electrical signal, and then extracting the same to an exterior location.
As such a radiographic imaging device, a radiographic imaging device having a scintilator layer containing a phosphor sensitive to radiation, an upper electrode and a lower electrode, an organic photoelectric conversion layer disposed between the upper electrode and the lower electrode and absorbing light emitted by the radiation incident on the scintilator layer and converting the same to a charge, and an insulating substrate having a storage capacitor and thin film transistor unit for reading the charge generated in the organic photoelectric conversion layer for each image detection pixel, is known (Japanese Patent Application Laid-Open (JP-A) No. 2009-32854).
It is no exaggeration to say that the diagnosis target in a radiographic image can be any portion of a human body, such as the internal organs, bones, muscles, or blood vessels. In order to obtain favorable images in desired portions, the dose of radiation emitted needs to be adjusted to an accurate numerical value.
In general, imaging is carried out while making the dose of radiation smaller for portions containing much water, such as internal organs, and making the dose of radiation larger for bones. As the characteristics of an X-ray tube, which is one radiation source, in the case of the same tube voltage and the same irradiation time, the dose of X-rays becomes larger when the energy of the X-rays is higher. The imaging conditions need to be determined while considering the above so that images of desired portions have sufficient gradation.
In contrast, the dose of radiation, such as X-rays, to be emitted to a human body needs to be made as small as possible, and re-imaging particularly needs to be avoided.
As a radiographic imaging device which automatically controls the dose of radiation, a device having a photodiode containing amorphous silicon which absorbs light emitted by radiation incident on an scintilator layer and converting the same to a charge formed in pixel units and a light detector for receiving light passing through a region between the pixel units, in which the dose of radiation is detected by the light detector and controlled, is known (see, for example, Japanese National Phase Publication No. 11-513122 and JP-A No. 10-284289).
As another radiographic imaging device which automatically controls the dose of radiation, a device additionally having a monitoring thin film transistor for detecting a voltage value generated by charges accumulated in a storage capacitor for image detection, in which information on the dose of X-rays of each pixel is obtained by the monitoring thin film transistor, and the dose of X-rays is controlled based on the information, is known (see, for example, JP-A No. 2004-97465).
However, in the radiographic imaging devices disclosed in Japanese National Phase Publication No. 11-513122 and JP-A No. 10-284289, a photodiode containing amorphous silicon divided for each pixel unit needs to be formed. Furthermore, it is necessary to provide another photoelectric conversion layer for performing photoelectric conversion of the light passing through the region between the pixel units and the photoelectric conversion characteristics of the amorphous silicon and the photoelectric transfer characteristics of the another photoelectric conversion layer are difficult to make the same. Thus, the dose of X-rays is not always controlled accurately.
In the radiographic imaging device disclosed in JP-A No. 2004-97465, the monitoring thin film transistor needs to additionally be provided for each image detection pixel, which complicates the radiographic imaging device.